Viscoelastic micellar solutions in nonionic fluorinated surfactant systems
Durga P Acharya1, Suraj Chandra Sharma, Carlos Rodriguez-Abreu
1Graduate School of Environment and Information Sciences, Yokohama National University, 79-7 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan.
The Journal of Physical Chemistry. B
|October 13, 2006
Summary
This study explores how temperature affects fluorinated wormlike micellar solutions. Increasing temperature initially boosts viscosity and micelle growth, but further increases lead to decreased viscosity and phase separation, impacting rheological properties.
Area of Science:
- Materials Science
- Physical Chemistry
- Colloid Science
Background:
- Viscoelastic wormlike micellar solutions are crucial in various applications.
- Understanding their behavior under changing conditions is essential for material design.
- Fluorinated surfactants offer unique properties for self-assembly.
Purpose of the Study:
- To investigate the formation and rheological behavior of a specific nonionic fluorinated surfactant solution.
- To elucidate the temperature-dependent structural and dynamic transitions of these micellar systems.
- To correlate microstructural changes with macroscopic rheological properties.
Main Methods:
- Rheological measurements (viscosity, shear modulus, relaxation time) as a function of temperature and surfactant concentration.
- Small-angle X-ray scattering (SAXS) for structural analysis of micellar aggregates.
- Dynamic light-scattering (DLS) to identify relaxation modes and network dynamics.
Main Results:
- Temperature-induced viscosity growth observed, peaking at T(eta)-max, followed by decrease and phase separation.
- SAXS confirmed cylindrical aggregate growth with temperature, with hints of lamellar structures at higher temperatures.
- Rheological parameters (G0, tauR) evolution correlated with microstructural changes; Maxwellian behavior observed.
- Surfactant concentration influences T(eta)-max and viscosity profiles.
- DLS revealed fast, medium, and slow relaxation modes, with slow modes disappearing at higher temperatures.
Conclusions:
- The study demonstrates a clear link between temperature, micellar microstructure, and bulk rheological properties.
- The observed transitions are characteristic of entangled wormlike micellar systems.
- Findings provide insights into the design and application of fluorinated viscoelastic solutions.
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